Such carriers are already known which include, for example, those shown in FIGS. 6 and 7.
The carrier shown in FIG. 6 will be described. The illustrated carrier comprises a body 1, a post 2 provided upright thereon, and a lift bar 4 disposed inside the post 2 and movable upward and downward. The lift bar 4 has a lower claw 5 and an upper claw 7 each pivoted at an intermediate portion thereof to the bar upper end. The two claws 5, 7 are interconnected, each at its one end, pivotably by a link 71. A cylinder device 3 is mounted on the carrier body 1 and has a piston rod 32 connected to the lift bar 4.
When the lift bar 4 is raised with the upper rim of a drum 9 held between the lower claw 5 and the upper claw 7, the load acting on the lower claw 5 causes the link 71 to move down the other end of the upper claw 7, i.e., the forward end thereof, permitting the two claws to tightly clamp the drum rim. The carrier body 1 is further provided with a contact portion 41 for preventing the drum from inclining forward by coming into contact with the trunk of the drum 9 when the drum 9 is lifted.
With the carrier described above, the contact portion 41 is fixed to the carrier body 1, so that the drum 9 is not liftable to a level at which the lower rim of the drum is positioned above the contact portion 41. Consequently, the carrier is unable to place the drum on a considerably high table.
Accordingly, carriers are proposed wherein the contact portion 41 is movable to varying levels like the one shown in FIG. 7. The illustrated carrier has a lift bar 4 connected to its body 1 by parallel links 23, 23 and provided with a lower claw 5 and an upper claw 7 like the foregoing carrier and with a lifting cylinder device 3 connected thereto.
With this carrier, however, the lift bar 4 moves forward or rearward when moving upward or downward since the lift bar 4 is supported by the parallel links 23, 23. This produces a difference between the position where the drum is lifted and the position where the drum is placed on the ground. Accordingly it is difficult to place four drums 9 on a pallet 8 without allowing any portion of the drum to project beyond the pallet as seen in FIG. 4. In the case where drums are transported as placed on pallets into a warehouse by an automated system, the drum 9, if partly projecting from the pallet 8, will actuate a safety circuit to stop the automatic operation. It is therefore the practice to manually push the projecting drum 9 to eliminate the projection. This requires labor.
Further when the drum 9 is lifted, a lower portion of the drum bears on the contact portion 41. At this time, a reaction F acts on the contact portion (see FIG. 8A). Assuming that the drum has a weight W, diameter D and height h, the reaction F is given by F=(D/2.times.W)/h and similarly acts on the clamping portions of the lower claw 5 and the upper claw 7. In the case of the conventional carriers shown in FIGS. 6 and 7, only the lift bar 4 bears the reaction F acting on the clamp portions, with the result that the reaction F acts as it is on the lift bar 4 as a bending moment. The lift bar 4 therefore needs to have rigidity to withstand this bending moment.
The present invention provides a carrier which is free of the above problems.